# MATHS

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Please show the quickest way to do this question?

Amanda has 20 coins in her purse. She has only 10c,20c and 50c coins, and their total value is \$5. If she has more 50c than 10c coins, how many 10c has she?

Thank You

• MATHS - ,

Are you in algebra using variables 'c'?

• MATHS - ,

I'm not sure what you mean.

• MATHS - ,

What grade are you in?

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YEAR 4

• MATHS - ,

c stands for cents?

• MATHS - ,

yes c stands for cents.

• MATHS - ,

I got 4 x 50c = \$2

2 x 10c = 20 c

14 x 20c = \$2.80c

so she has 2 x 10c

• MATHS - ,

Since you are in year 4, you will be able to solve this algebraically.
let the number of 10c pieces be x
let the number of 20c pieces be y
let the number of 50c pieces be (20-x-y)

10x + 20y + 50(20-x-y) = 500
reduces to
4x + 3y = 50
so we need positive integer solutions for x and y
clearly x has to be between 0 and 13
after only two tries, I got
x = 2, and y = 14
then
number of 10c pieces = 2
number of 20c pieces = 14
number of 50c pieces = 20-2-14 = 4

check: 2x10 + 14x20 + 4x50 = 500

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